Breastfeeding practices in two Brazilian metropolitan areas (S. Paulo and Recife) are described, as part of a study carried out in 1987. In a random sample of healthy 0-8 month old infants, selected from all health care units, higher breastfeeding rates were found in S. Paulo (initiation, prevalence, median and average) than in Recife. The mean duration of breastfeeding, mixed and full, was of 127.5 and 66.6 days, respectively, for S. Paulo, and of 104.4 and 31.7 days for Recife. When data are analysed according to ethnic group, white S. Paulo women breastfeed more than white Recife women. Full breastfeeding rate is more prevalent among white and "mulato" S. Paulo women. However, when the data were analyzed for each city separately, it was found, remarkably, that the non-whites breastfeed more than the whites. In Recife, full breastfeeding is particularly low in whites (of 15.3 days median) and "mulatos" (of 16.7 days), but of 34.5 days in blacks. The study points out the need for greater in-depth investigation of the issue of ethnicity and infant feeding practices, still inadequately understood in world literature.